This invention relates to laser nozzles and optical cavity walls. Two patents which show nozzle assemblies of the wafer type with a nozzle cavity being included in one are U.S. Pat. No. 3,602,432 and U.S. Pat. No. 3,819,321. An entire laser system with flow from a combustor through a plurality of nozzles into a lasing region with reflecting walls is shown in U.S. Pat. No. 3,665,336.